for an all-purpose ride, what you're looking for is a good mix of stick definition and wash, and also perhaps a balance of ride characteristics and crash capability. you want the cymbal to sound good whether you're playing its bow, bell, or edge.
generally speaking, medium weight rides are the best examples of the above. of course, this is not always the case. for example, zildjian's 21" a sweet ride is medium weight but is too washy for heavier music. on the other hand, sabian's 20" hhx evolution ride is a thinner cymbal (about medium light) but is extremely versatile.
with that said, the 22" k custom medium is a good choice. it has all the above qualities (maybe lacking in the bell department, but this is on a case to case basis), and no, it isn't too dark for rock. for metal, maybe, but for straight up rock it should do fine.